Cardiac rhythm management system with staggered pulses for coordination therapy

ABSTRACT

A cardiac rhythm management system for coordination therapy includes a pulse generator to generate pacing and discharging of recharge pulses. A pulse delivery controller coupled to the pulse generator, times the delivery of the pacing and discharging of recharge pulses in a desired sequence. A therapy circuit coupled to the pulse delivery controller, receives the timed pulses from the pulse delivery controller and delivers the timed pulses to one or more electrodes disposed in or around a heart to communicate the timed pacing and discharging of recharge pulses to different sites of a heart, to avoid any interactions resulting from the electric fields surrounding the electrodes during a multiple site pacing required by the coordination therapy.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to cardiac rhythm management systems,and particularly, but not by way of limitation, to a cardiac rhythmmanagement system, that provides staggered non-overlapping pulses forcoordination therapy.

BACKGROUND

When functioning properly, the human heart maintains its own intrinsicrhythm, and is capable of pumping adequate blood throughout the body'scirculatory system. However, some people have irregular cardiac rhythms,referred to as cardiac arrhythmias. Such arrhythmias result indiminished blood circulation. One mode of treating cardiac arrhythmiasuses drug therapy. Drugs are often effective at restoring normal heartrhythms. However, drug therapy is not always effective for treatingarrhythmias of certain patients. For such patients, an alternative modeof treatment is needed. One such alternative mode of treatment includesthe use of cardiac rhythm management system. Such a system may beimplanted in a patient to deliver therapy to their heart.

Cardiac rhythm management systems include, among other things,pacemakers. Pacemakers deliver timed sequences of low energy electricalstimuli, called pace pulses, to the heart, such as via a transvenouslead wire or catheter (referred to as a “lead”) having one or moreelectrodes disposed in or about the heart. Heart contractions areinitiated in response to such pace pulses (this is referred to as“capturing” the pacing heart). By properly timing the delivery of pacepulses, the heart can be induced to contract in proper rhythm, greatlyimproving its efficiency as a pump. Pacemakers are often used to treatpatient's hearts exhibiting bradyarrhythmias, that is, hearts that beattoo slowly.

Cardiac rhythm management systems also include cardioverters ordefibrillators that are capable of delivering higher energy electricalstimuli to the heart. Defibrillators may be used to treat patient'shearts exhibiting tachyarrhythmias, that is, hearts that beat too fast.Such too-fast heart rhythms also cause diminished blood circulationbecause the heart isn't allowed sufficient time to fill with bloodbefore contracting to expel the blood, resulting in the heart pumping areduced amount of blood. Such pumping by the heart is inefficient. Adefibrillator is capable of delivering a high energy electricalstimulus. The high energy electrical stimulus interrupts thetachyarrhythmia, allowing the heart to reestablish a normal rhythm forthe efficient pumping of blood. In addition to pacemakers, cardiacrhythm management systems also include, among other things,pacer/defibrillators that combine the functions of pacemakers anddefibrillators, drug delivery devices, and any other systems or devicesfor diagnosing or treating cardiac arrhythmias.

Cardiac rhythm management systems are also used in the treatment ofcongestive heart failure. Congestive heart failure can occur when theleft and right ventricles do not contract simultaneously, but rather,they contract one ventricle after the other ventricle. This reduces thepumping efficiency of the heart. Moreover, in the case of left bundlebranch block, for example, different regions within the left ventriclemay not contract together in a coordinated fashion. Generally congestiveheart failure can be treated by biventricular coordination therapy thatprovides pacing pulses to both right and left ventricles. See. e.g.,Mower, U.S. Pat. No. 4,928,688. Normally, intrinsic signals originate inthe sinoatrial node in the upper right atrium, traveling through anddepolarizing the atrial heart tissue such that resulting contractions ofthe right and left atria are triggered. The intrinsic atrial heartsignals are received by the atrioventricular node which, in turn,triggers a subsequent ventricular intrinsic heart signal that travelsthrough and depolarizes the ventricular heart tissue such that resultingcontractions of the right and left ventricles are triggeredsubstantially simultaneously.

One problem faced by cardiac rhythm management systems in treatingcongestive heart failure is that, coordination therapy may requireissuing stimulation pace pulses simultaneously in more than one regionof a heart to ensure these regions contract in a coordinated manner. Forexample, coordination therapy may require applying pacing stimulation toone or both ventricles or multiple sites within one or more ventriclesin a pattern that coordinates the ventricular contraction sequence. Suchtherapy is believed to improve systolic function of patients withventricular conduction disorders. During simultaneous pacing of multipleregions of the heart, the resulting electric fields generated betweenthe pacing sites may interact. This may result in unwanted andunexpected currents between the pacing electrodes at different sitessuch as different chambers of the heart and can affect the ability ofthe pacing pulses to capture the heart at the simultaneous pacing sites.Such interactions can become greater when the coordination pacing pulseshave different voltage amplitudes due to the resulting electric fieldsbetween the pacing sites. Another problem with issuing biventricularcoordination pace pulses simultaneously in more than one chamber is thatthese interactions can result in very inefficient pacing methods, oneexample being that it may transform cathodal pacing pulse into anodalpacing pulse.

These interactions can increase when a bipolar right ventricularelectrode configuration is used with a single left ventricularelectrode. In this configuration, one of the right ventricularelectrodes provides a common return path, for the right and leftventricular stimulations. During such interactions, the simultaneousbiventricular capture cannot be assured if left ventricular and rightventricular capture is tested separately.

When the pace pulses are delivered to a heart, leftover charge (rechargepulses) from pacing regions is discharged from the heart. These rechargepulses may also interact with pace pulses or other recharge pulses atdifferent heart locations. This too may result in unwanted interactionsbetween different sites.

Generally simultaneous pacing of multiple regions of a heart can beadvantageous in the treatment of congestive heart failure, however; suchsimultaneous pacing at different pacing sites may result in unwantedinteractions between different pacing sites. These interactions mayresult in undesirable results, such as loss of capture at the pacingsites. Thus, there is a need to eliminate unwanted interactions betweenelectrodes at different pacing sites of a heart.

SUMMARY

The above mentioned shortcomings, disadvantages and problems areaddressed by the present subject matter, which will be understood byreading and studying the following specification. The present subjectmatter provides, among other things, a cardiac rhythm management systemthat eliminates interactions between electrodes at multiple pacing sitesof a heart. This is accomplished by providing an offset between adjacentpacing and/or recharge pulses to electrodes in various regions of aheart to eliminate the interactions at different pacing sites. Thisimproves the treatment for congestive heart failure by providing therequired/programmed level of energy to the pacing sites. The presentsystem provides an offset between pulses to eliminate the interactionsduring unichamber, bichamber, or multisite pacing with or withoutintersite stimulation delays to restore proper coordination betweendifferent chambers and between different intra chamber regions of theheart.

According to one aspect of the present subject matter, a pulse deliverycontroller receives pulses from a pulse generator and then delivers thepulses to multiple electrodes located at different pacing sites in adesired sequence to avoid any interactions between electric fieldssurrounding the electrodes during pulsing at different pacing sites.After delivering the pacing pulses, discharging of the recharge pulsesbegins from the respective pacing sites. During discharging, the pulsedelivery controller further offsets recharge pulses to eliminateinteractions between recharge and pacing pulses. Similar pulsesequencing takes place every subsequent cardiac cycle interval.

In one embodiment of providing coordination therapy, the system issues atime delay between the left and right ventricular pacing and rechargepulses to avoid any interactions between the leads. In anotherembodiment, the system issues a time delay between pulses (pace and/orrecharge) associated with the right atrial, and right ventricular leads,and a time delay between pulses associated with right and leftventricular pulses to avoid any interactions between these leads. Inanother embodiment the system issues a time delay between pulsesassociated with left cardiac chamber electrode and the right cardiacchamber electrode to avoid any interactions between these leads. Inanother embodiment the system issues a time delay between pulsesassociated with right cardiac chamber electrode and the left cardiacchamber electrode to avoid any interactions between these leads.

Other aspects of the present subject matter will be apparent on readingthe following detailed description of the invention and viewing thedrawings that form a part thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating generally one embodiment ofportions of a cardiac rhythm management system and an environment inwhich it is used.

FIG. 2 is a schematic drawing illustrating generally one embodiment ofportions of a cardiac rhythm management system coupled to a heart byleft and right ventricular electrodes.

FIG. 3 is a schematic/block diagram illustrating generally oneembodiment of portions of a cardiac rhythm management system showinginterconnections between major functional components of the cardiacrhythm management device when using right and left ventricularelectrodes coupled to a heart.

FIG. 4 is a schematic illustrating generally, by way of example, oneembodiment of an offset issued by a pulse delivery controller betweenthe pacing pulses associated with first and second electrodes.

FIG. 5 is a schematic illustrating generally, by way of example, oneembodiment of ranges of time delays and pulse duration issued duringleft and right ventricular pacing and discharging of recharge pulses.

FIG. 6 is a schematic drawing illustrating generally, by way of example,one embodiment of time offsets used in a cardiac rhythm managementsystem.

FIG. 7 is a flow chart illustrating generally, by way of example, anembodiment of the steps of providing a coordinated therapy.

FIG. 7A is a flow chart illustrating generally, by way of example,another embodiment of the steps of providing a coordinated therapy.

FIG. 8 is a flow chart illustrating generally, by way of example,another embodiment of the steps of providing a coordinated therapy.

FIG. 9 is a schematic drawing illustrating generally, by way of example,an embodiment of using a cardiac rhythm management system coupled to aheart by right atrial, right ventricular, and left ventricularelectrodes for pacing these chambers of the heart.

FIG. 10 is a schematic/block diagram illustrating generally anotherembodiment of portions of a cardiac rhythm management system showinginterconnections between major functional components of the device whenusing right atrial, right ventricular and left ventricular electrodescoupled to a heart.

FIG. 11 is a schematic illustrating generally, by way of example, theranges of time offsets and pulse durations issued between pulses (paceand/or recharge) associated with the right atrial, and right ventricularleads, and between pulses associated with right and left ventricularpulses to avoid any interactions between the leads.

FIG. 12 is a schematic illustrating generally, by way of example, oneembodiment of time offsets issued between a right atrial and rightventricular, and right and left ventricular pacing, and discharging of arecharge pulses associated with the pacing pulses to avoid anyinteractions between the leads and to provide a coordinated therapy to aheart.

FIG. 13 is a flow chart illustrating generally, way of example, anotherembodiment of providing a coordinated therapy to a heart.

FIG. 14 is a schematic drawing illustrating generally one example ofinteractions taking place between electric fields at two pacing sites.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents. In theaccompanying drawings, like numerals describe substantially similarcomponents throughout the several views. Like numerals having differentsuffixes represent different instances of substantially similarcomponents.

In this document, the term “offset” means, first and second pulsesdelivered to electrodes in various regions of a heart are timed suchthat there is a fractional time delay between an end of the delivery ofthe first pulse and a beginning of delivery of the second pulse suchthat the pulses are substantially simultaneous yet non-overlapping, toavoid any interactions between electric fields at various pacing sites,and to provide the required/programmed coordinated therapy.

In this document, the term “pulse delivery controller” is understood asthe controller delivering the offset pulses to the electrodes in adesired sequence to avoid any interactions between electric fieldsduring pulsing at various pacing sites. The term “timer” is alsounderstood as the timer providing the offset pulses to the electrodes inthe desired sequence to avoid interactions between electric fieldsduring pulsing at various pacing sites.

Also in this document, the term “discharging of recharge pulse” isunderstood as, removal of an accumulated charge within the system orcardiac tissue, by generally reversing the current through the pacingcircuit via a low amplitude, low duration recharge pulse.

The present methods and apparatus will be described in applicationsinvolving implantable medical devices including, but not limited to,implantable cardiac rhythm management systems such as pacemakers,cardioverter/defibrillators, pacer/defibrillators, and biventricular orother multi-site coordination devices. However, it is understood thatthe present methods and apparatus may be employed in unimplanteddevices, including, but not limited to, external pacemakers,cardioverter/defibrillators, biventricular or other multi-sitecoordination devices, monitors, programmers and recorders.

This document describes, among other things, a cardiac rhythm managementsystem providing a method and apparatus for offsetting butnon-overlapping the pacing and recharge pulses to eliminate unwantedinteractions between electrodes at various pacing sites.

One problem faced by cardiac rhythm management systems is that thecoordination therapy may require issuing stimulation pace pulsessimultaneously in more than one region of a heart to ensure theseregions contract in a coordinated manner. For example, coordinationtherapy may require applying pacing stimulation to one or bothventricles or multiple sites within one or more ventricles in a patternthat coordinates the ventricular contraction sequence. Such therapy isbelieved to improve systolic function of patients with ventricularconduction disorders. During simultaneous pacing of multiple regions ofthe heart, the resulting electric fields generated between the pacingsites may interact. This may result in unwanted and unexpected currentsbetween the pacing electrodes at different sites such as differentchambers of the heart. Such interactions can have great implicationswhen the coordination pacing pulses have different voltage amplitudesdue to the resulting electric fields between the pacing sites. One suchimplication with issuing biventricular coordination pace pulsessimultaneously in more than one chamber is that these interactions maytransform cathodal pacing pulse into anodal pacing pulse.

The problem of interactions between pacing electrodes can become evengreater when a bipolar right ventricular electrode configuration is usedwith a single left ventricular electrode. In such configuration, one ofthe right ventricular electrodes provides a common return path, for theright and left ventricular stimulations. Also due to these interactions,the simultaneous biventricular capture cannot be assured if leftventricular and right ventricular capture is tested separately.

Therefore, the present system advantageously delivers offset pacingpulses that are as close in time as feasible and yet non-overlapping toprovide the required coordination therapy. Also the systemadvantageously offsets the discharging of the recharge pulses associatedwith the pacing pulses to eliminate any interactions between electricfields associated with pacing and recharge pulses. In one embodiment,the offset between pacing pulses is so small and physiologicallyinsignificant that the propagation of resulting depolarization atdifferent heart chambers are still acceptable to generate coordinatedcontraction of cardiac chambers. In one example, a three millisecondnon-overlapping offset between the end of delivery of right cardiacchamber pacing pulse and the beginning of delivery of left cardiacchamber pacing pulse is sufficient to generate simultaneous contractionof the two cardiac chambers, and also this offset is sufficient to avoidany unwanted interactions between electrodes during pacing.

FIG. 1 is a schematic drawing illustrating generally, by way of example,but not by way of limitation, one embodiment in which the cardiac rhythmmanagement system is used. In FIG. 1, system 100 includes an implantablecardiac rhythm management device 105, also referred to as an electronicsunit, which is coupled by an intravascular endocardial lead 110, orother lead, to a heart 115 of patient 120. System 100 also includes anexternal programmer 125 providing wireless communication with device 105using a telemetry device 130. Catheter lead 110 includes a proximal end135, which is coupled to device 105, and a distal end 140, which iscoupled to one or more portions of heart 115.

FIG. 2 is a schematic drawing illustrating generally, by way of example,but not by way of limitation, one embodiment of device 105 coupled byleads 110A and 110C to a heart 115, which includes a right atrium 205, aleft atrium 210, a right ventricle 200 and a left ventricle 215. Device105 includes components that are enclosed in a hermetically sealedenclosure, such as can 250. Additional electrodes may be located on thecan 250, or on an insulating header 255, or on portions of device 105,for providing pacing and/or defibrillation energy in conjunction withthe electrodes disposed in or around heart 115. In this embodiment,right ventricular lead 110A includes electrodes (electrical contacts)disposed in, around, or near right ventricle 200 of heart 115, such asring electrode 140A or tip electrode 220A for delivering pacing therapyto the ventricle 200. Also in this embodiment is shown, left ventricularlead 110C disposed in, around, or near left ventricle 215 of the heart115, such as tip electrode 220C or ring electrode 140C for deliveringpacing therapy to the heart 115. The present method and apparatus willwork in a variety of configurations and with a variety of electricalcontacts or “electrodes.”

FIG. 3 is a schematic/block diagram illustrating generally, by way ofexample, but not by way of limitation, one embodiment of portions ofdevice 105, coupled to a heart 115. In this embodiment, device 105includes power source 300, left and right ventricular sensing circuits330 and 310, a left ventricular a ventricular therapy circuits 340 and320 providing coordination therapy to the heart, as appropriate, throughthe electrodes located at or near the ventricles 200 and 215, from apulse delivery controller 325.

Right and left ventricular sensing circuits 310 and 330 are coupled byright and left ventricular leads 110A and 110C to the heart 115 forreceiving, sensing, and/or detecting ventricular activations (alsoreferred to as ventricular depolarizatons or R-waves), which correspondto ventricular contractions. Such ventricular heart signals includenormal ventricular rhythms, and abnormal fibrillation, and otherventricular activity, such as irregular ventricular contractionsresulting from conducted signals from atrial fibrillation. Ventricularsensing circuits provide one or more signals to pulse deliverycontroller 325 indicating, among other things, the presence ofventricular depolarizations, whether regular or irregular in rhythm.

Ventricular therapy circuits 320 and 340 provide ventricular pacingtherapy, as appropriate, to electrodes located at or near the ventricles200 and 215 of the heart 115 for obtaining resulting evoked ventriculardepolarizations.

The pulse delivery controller 325, controls the delivery of coordinationtherapy, and provides the offset and non overlapping pacing pulses tothe left and right ventricular electrodes, based on heart signalsreceived from left and right ventricular sensing circuits 330 and 310.Pulse delivery controller 325 includes various modules, which areimplemented either in hardware or as one or more sequences of stepscarried out on a microprocessor or other microcontroller. It isunderstood that the various modules of pulse delivery controller 325need not be separately embodied, but may be combined or otherwiseimplemented differently, such as in software/firmware.

In general terms, sensing circuits 310 and 330 sense electrical signalsfrom heart tissue in contact with the catheter leads 110A and 110C towhich these sensing circuits 310 and 330 are coupled. Sensing circuits310 and 330 and/or pulse delivery controller 325 process these signals.Based on these sensed signals, pulse delivery controller 325 issuescontrol signals to therapy circuits, such as ventricular coordinationtherapy circuits 320 and 340, if necessary, for the delivery ofelectrical energy (e.g., pacing and/or defibrillation pulses) to theappropriate electrodes of leads 110A and 110C. Pulse delivery controller325 may include a microprocessor or other form of controller forexecution of software and/or firmware instructions. The software of thepulse delivery controller 325 may be modified (e.g., by remote externalprogrammer 125) to provide different parameters, modes, and/or functionsfor the implantable device 105 or to adapt or improve performance ofdevice 105.

In one further embodiment, one or more sensors, such as sensor 370, mayserve as inputs to pulse delivery controller 325 for adjusting the rateat which pacing or other therapy is delivered to heart 115. One suchsensor 370 includes an accelerometer that provides an input to pulsedelivery controller 325 indicating increases and decreases in physicalactivity, for which pulse delivery controller 325 increases anddecreases pacing rate, respectively. Another such sensor includes animpedance measurement, obtained from body electrodes, which provides anindication of increases and decreases in the patient's respiration, forexample, for which pulse delivery controller 325 increases and decreasespacing rate, respectively. Any other sensor 370 providing an indicatedpacing rate can be used.

FIG. 4 is a schematic illustrating generally, by way of example, but notby way of limitation, one embodiment of issuing an offset ‘Δt’ by thepulse delivery controller 325 between the end 420 of delivery of firstpacing pulse 400 and beginning 430 of delivery of a second pacing pulse410 to avoid any interactions between the first and second pacing pulsesduring a coordination therapy. This offset ‘Δt’ is generally a verysmall fractional time of a single cardiac cycle interval, andphysiologically insignificant (offset ‘Δt’ is about 2 to 10 millisecondsin a cardiac cycle interval ranging between 324 to 2000 milliseconds),such that the propagation of resulting depolarizations at differentheart chambers are still acceptable to generate coordinated contractionof heart chambers. Also shown is an offset between discharging ofrecharge pulses 440 and 450 associated with the first and second pacingpulses introduced by the pulse delivery controller 325 to avoid anyinteractions during the discharging of the recharge pulses 440 and 450.In one embodiment, the discharging of the recharge pulses takes placebetween pacing pulses as time allows and completing any unfinishedportion after the pacing pulse with appropriate offsets in between thepacing and recharge pulses to avoid any interactions.

FIG. 5 is a schematic illustrating generally, by way of example, but notby way of limitation, one embodiment of offset Δ_(t4) introduced betweenthe left and right ventricular pacing pulses 500 and 510 of about 2 to10 milliseconds to avoid any interactions between electric fieldssurrounding the electrodes. Also shown in this embodiment, by way ofexample, are the pacing pulse duration Δ_(t3) ranging between 0.05 to 2milliseconds, the recharge pulse 540 duration Δ_(t2) ranging between 5to 50 milliseconds, and the cardiac cycle interval Δ_(t1) rangingbetween 324 to 2000 milliseconds to avoid interactions between electricfields surrounding the electrodes during pacing 500 and 510 anddischarging of recharge pulses 540 and 550 at various pacing sites of aheart.

FIG. 6 is a schematic illustrating generally, by way of example, but notby way of limitation, one embodiment of a three millisecond offsetissued between the right and left ventricular pacing pulses to generatethe simultaneous contraction of the two heart chambers, and to avoid anyunwanted interactions between electrodes during a coordination therapy.

FIG. 7 is a flow chart, illustrating generally, by way of example, butnot by way of limitation, one embodiment 700 of the various stepsincluded in providing a coordinated therapy to a heart. Upon generatingfirst and second pacing pulses 710 and 720, a pulse delivery controllerdelivers the first pacing pulse 730, and then deliver the second pacingpulse having an offset between the end of delivery of the first pacingpulse and the beginning of delivery of the second pacing pulse toprovide a coordinated therapy 740.

FIG. 7A is a flow chart, illustrating generally, by way of example, butnot by way of limitation, one embodiment of the various steps includedin providing a coordinated therapy to a heart 750. Upon generating rightand left cardiac chamber pacing pulses 760 and 770, a pulse deliverycontroller delivers the right cardiac chamber pacing pulse 780, and thendelivers the left cardiac chamber pacing pulse at least 2 to 10milliseconds after completing the delivery of the right cardiac chamberpacing pulse to a heart to avoid any interactions between the electricfields surrounding the electrodes during the right and left cardiacchamber pacing 790. In one embodiment, after completing the delivery ofthe left ventricular pacing pulse, the pulse deliver controller,discharges right and left cardiac chamber recharge pulses such that thedischarge of the recharge pulse are non-overlapping with the right andleft cardiac chamber pacing pulses. In one embodiment the discharging ofthe recharge pulses takes place between pacing pulses as time allows andcompleting any unfinished portion after the pacing pulse.

FIG. 8 is a flow chart, illustrating generally, by way of example, butnot by way of limitation, another embodiment 800 of the various stepsincluded in providing a coordinated therapy to a heart. The first stepin the process of providing the coordinated therapy to the heartincludes generating a right ventricle pacing pulse having a pulseduration of about 0.05 to 2 milliseconds 810. Then generating a leftventricle pacing pulse having a pulse duration of about 0.05 to 2milliseconds 820. After generating the right and left ventricle pacingpulses, a pulse delivery controller delivers the right ventricle pacingpulse to a right ventricular chamber of a heart at 830. The pulsedelivery controller then delivers the left ventricle pacing pulse to aleft ventricular chamber of the heart such that it is 2 to 10milliseconds after delivering the right ventricle pacing pulse to theheart, and further the right and left ventricle pacing pulses aresubstantially simultaneous and non-overlapping to avoid any interactionsbetween electric fields surrounding the electrodes during pacing 840.Then the pulse delivery controller discharges right and left ventriclerecharge pulses, such that the right and left ventricle recharge pulsesare non-overlapping with the right and left ventricle pacing to avoidany interactions between surrounding electrodes during discharging 850.

FIG. 9 is a schematic drawing, similar to FIG. 2, illustratinggenerally, by way of example, but not by way of limitation, anotherembodiment of device 105 coupled by a right atrial lead 110B to a heart115, in addition to the ventricular leads 110A and 110C shown in FIG. 2,which includes a right atrium 205. In this embodiment, right atrial lead110B includes electrodes (electrical contacts) disposed in, around, ornear right atrium 205 of the heart 115, such as tip electrode 220B fordelivering pacing therapy to the right atrium 205. The present methodand apparatus will work in a variety of other configurations and with avariety of other electrical contacts or “electrodes.”

FIG. 10 is a schematic/block diagram, similar to FIG. 3, illustratinggenerally, by way of example, but not by way of limitation, anotherembodiment of portions of device 105, showing an atrial lead 110Bcoupled to a heart 115, in addition to the ventricular leads 110A and110C shown in FIG. 3. Also shown is a atrial therapy circuit 360 andatrial a sensing circuit 350 connected via bus 327 to a programmablecontroller 325 for providing the coordination therapy to the heart. Theprogrammable controller 325 provides staggered, nearly close, andnon-overlapping pacing and recharge pulses to all three electrodes110A-C.

FIG. 11 is a schematic, similar to FIG. 5, illustrating generally, byway of example, but not by way of limitation, another embodiment of theranges of offsets and pulse durations used in providing an offsetbetween the delivery of right atrial, left ventricle, and rightventricle pacing and discharging of associated recharge pulses to avoidany interaction between the electric fields surrounding the electrodesduring pacing and discharging of the recharge pulses. FIG. 11, inaddition to what is shown in FIG. 5, generally shows, by way of example,one embodiment of the offset Δ_(t7) between 10 to 400 milliseconds usedbetween right atrial pacing pulse and the right ventricle pacing pulseto provide coordination therapy. Also shown in this embodiment, by wayof example, are the right atrial pacing pulse 1160 duration 66 t₆, therecharge pulse 1170 duration Δt₅, and the offset Δt₄ introduced betweenthe left and right ventricular pacing pulses 500 and 510.

FIG. 12 is a schematic, similar to FIG. 6, illustrating generally, byway of example, but not by way of limitation, one embodiment of issuingan offset of three milliseconds between right and left ventricularpacing pulses, and a 50 millisecond offset issued between the rightatrial and right ventricular pacing pulses to generate contractions ofthree heart chambers, and to avoid any unwanted interactions betweenelectric fields surrounding the electrodes at the three heart chambersduring a coordination therapy. Also shown are one embodiment of atrialpacing pulse duration of 0.5 milliseconds and the atrial recharge pulseduration of 25 milliseconds.

FIG. 13 is a flow chart, similar to FIG. 8, illustrating generally, byway of example but not by way of limitation, another embodiment of thevarious steps included in providing a coordinated therapy to a heart.The first step in the process of providing the coordinated therapy tothe heart includes generating a right atrium, right ventricle and leftventricle pacing pulses 1310, 1320, and 1330. After generating thepacing pulses, a pulse delivery controller delivers the right atriumpacing pulse to a right atrium chamber of a heart 1340. Then the pulsedelivery controller discharges a recharge atrium pulse after completingthe delivery of the right atrium pulse such that the recharge and thepacing pulses are non-overlapping to avoid any interactions betweenelectric fields surrounding the electrodes during pacing and discharging1350. After discharging the recharge atrium pulse, the pulse deliverycontroller delivers the right ventricle pacing pulse to the rightventricular chamber of the heart 1360. Then the pulse deliverycontroller deliver the left ventricle pacing pulse to the leftventricular chamber of the heart at least 2 to 10 milliseconds afterdelivering the right ventricle pacing pulse such that the right and leftventricle pulses are substantially simultaneous and non-overlapping toavoid any interactions between electric fields surrounding theelectrodes during pacing 1370. Then the pulse delivery controllerdischarges recharge right and left ventricular pulses from the right andleft ventricular chambers of the heart such that they arenon-overlapping to avoid any interactions between electric fieldssurrounding the electrodes during pacing and discharging 1380.

FIG. 13 is a flow chart, similar to FIG. 7, illustrating generally, byway of example but not by way of limitation, another embodiment of thesteps of providing a coordinated therapy to a heart. In addition to whatis shown in FIG. 7, FIG. 13 includes the steps of delivering anddischarging right atrium pacing and recharge pulses.

FIG. 14 is a schematic drawing showing generally one embodiment of anunwanted interactions 1130 taking place between the electric fields 1110and 1120 surrounding the right ventricular lead 220A and leftventricular lead 220C, during simultaneous pacing of both theventricles.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

CONCLUSION

The above-described system provides, among other things, an offsetbetween pacing and recharge pulses using a pulse delivery controllerduring a coordination therapy. The pulse delivery controller, by issuingpulses and discharging recharge pulses in a desired sequence eliminatesany interactions resulting between electric fields surroundingelectrodes at different pacing sites of a heart. This issuing of pulsesin a desired sequence ensures providing a required/programmed level ofenergy to the electrodes during a coordination therapy.

What is claimed is:
 1. A cardiac rhythm management system, comprising: apulse generator, for generating pulses; a first cardiac chamberelectrode, coupled to the pulse generator, for delivering a first pulse,wherein the first pulse has a beginning and an end; a second cardiacchamber electrode, coupled to the pulse generator, for delivering asecond pulse, wherein the second pulse has a beginning and an end; and apulse delivery controller, coupled to the pulse generator, wherein thepulse delivery controller generates an offset between the end ofdelivery of the first pulse and the beginning of delivery of the secondpulse such that the first and second pulses are substantiallysimultaneous and non-overlapping.
 2. The system of claim 1, wherein thepulse generator generates pacing pulses.
 3. The system of claim 1,wherein the pulse generator generates discharging recharge pulses. 4.The system of claim 1, wherein the first cardiac chamber is associatedwith right atrial and right ventricular chambers of a heart.
 5. Thesystem of claim 1, wherein the second cardiac chamber is associated withleft atrial and left ventricular chambers of a heart.
 6. The system ofclaim 1, wherein the offset is approximately in the range of 2milliseconds to 10 milliseconds.
 7. The system of claim 1, wherein thefirst cardiac chamber is associated with right atrial and ventricularchambers of a heart, and wherein the left cardiac chamber is associatedwith left atrial, and left ventricular chambers of the heart.
 8. Thesystem of claim 7, wherein at least one of the right and left atrialelectrodes is a bipolar electrode and the other of the first and secondelectrodes is a unipolar electrode.
 9. The system of claim 7, where aconfiguration of electrodes is selected from the group consisting of:(1) a bipolar right ventricular electrode and a unipolar leftventricular electrode, (2) a bipolar left ventricular electrode and aunipolar right ventricular electrode, (3) a bipolar right ventricularelectrode and a bipolar left ventricular electrode, and (4) a unipolarright ventricular electrode and a unipolar left ventricular electrode.10. The system of claim 7, in which the offset between the end ofdelivery of the left ventricular pulse and the beginning of delivery ofthe right ventricular pulse is approximately in the range of about 2milliseconds to 10 milliseconds.
 11. The system of claim 7, in which theoffset between the end of delivery of the left atrial pulse and thebeginning of delivery of left ventricular pulse is approximately in therange of about 2 milliseconds to 10 milliseconds.
 12. The system ofclaim 7, in which the offset between the end of delivery of the rightatrial and the beginning of delivery of the right ventricular pulses isapproximately in the range of about 10 milliseconds to 400 milliseconds,and the offset between the end of delivery of the right ventricular andthe beginning of delivery of the left ventricular pulses isapproximately in the range of about 2 milliseconds to 10 milliseconds.13. The system of claim 1, wherein the pulse delivery controllercomprises a timer, wherein the timer generates an offset between thedelivery of a first pulse associated with the first electrode and thedelivery of a second pulse associated with the second electrode suchthat the pulses are substantially close and non-overlapping.
 14. Acardiac rhythm management system, comprising: a pulse generator forgenerating pacing pulses, and discharging recharge pulses; first,second, and third electrodes, coupled to the pulse generator, where thefirst electrode adapted for being associated with a right ventricle of aheart, second electrode adapted for being associated with a leftventricle of the heart, and the third electrode adapted for beingassociated with a right atrium of the heart; and a timer, coupled to thepulse generator, where the timer times delivery of the pacing pulsessuch that the pacing pulses associated with the first electrode areoffset but non-overlapping with the pacing pulses associated with thesecond electrode, and the pacing pulses associated with the thirdelectrode is offset but non-overlapping with the first and secondelectrodes, and wherein the timer further times discharging of therecharge pacing pulses associated with the pacing pulses of the first,second and third electrodes such that the discharging of recharge pulsesare offset but non-overlapping with the recharge and pacing pulses ofthe first, second and third electrodes.
 15. A cardiac rhythm managementsystem, comprising: pulse generator means; a first cardiac chamberelectrode coupled to the pulse generator means for delivering a firstpulse, wherein the first pulse has a beginning and an end; a secondcardiac chamber electrode coupled to the pulse generator means fordelivering a second pulse, wherein the second pulse has a beginning andan end; and means for generating an offset between the end of deliveryof the first pulse and the beginning of delivery of the second pulsesuch that the first and second pulses are substantially simultaneous andnon-overlapping.
 16. A method, comprising: generating a first pacingpulse for a first cardiac chamber of a heart, where the first pacingpulse includes a beginning and an end; generating a second pacing pulsefor a second cardiac chamber of the heart, where the second pacing pulseincludes a beginning and an end; and delivering the first and secondpacing pulses to the first and second cardiac chambers of the heartrespectively, wherein there is an offset between the end of delivery ofthe first pacing pulse and the beginning of delivery of the secondpacing pulse, wherein the first and second pacing pulses aresubstantially simultaneous and non-overlapping.
 17. The method of claim16, wherein the first and second cardiac chambers are associatedrespectively with the right and left atrial chambers of the heart. 18.The method of claim 16, wherein the first and second cardiac chambersare associated respectively with the right and left ventricular chambersof the heart.
 19. The method of claim 16, wherein the first and secondpacing pulses are associated respectively with the right and leftventricular chambers of the heart, and further the first and secondpacing pulses are associated with right and left atrial chambers of theheart.
 20. The method of claim 16, wherein delivering the first andsecond pacing pulses includes an offset approximately in the range of 2milliseconds to 10 milliseconds between the end of delivery of the firstatrial pacing pulse and the beginning of delivery of the second atrialpacing pulse.
 21. A method of delivering a coordinated pacing therapy toa heart, the method comprising: generating a right ventricular pacingpulse having a pulse duration approximately in the range of 0.05milliseconds to 2 milliseconds; generating a left ventricular pacingpulse having a pulse duration of approximately in the range of 0.05milliseconds to 2 milliseconds; delivering the right ventricular pacingpulse to the right ventricular chamber of a heart; delivering the leftventricular pacing pulse to the left ventricular chamber of the heartsuch that it is greater than or equal to 2 milliseconds and less than orequal to 10 milliseconds after delivering the right ventricular pacingpulse to the heart, wherein the right and left ventricular pacing pulsesare substantially simultaneous and non-overlapping; and dischargingright and left ventricular recharge pulses, wherein the discharging ofthe right and left ventricular recharge pulses are non overlapping, andwherein the discharging of the recharge pulses are further nonoverlapping with the right and left ventricular pulses.
 22. A method ofdelivering a coordinated pacing therapy to a heart, the methodcomprising: generating a right atrial pacing pulse for a right atriumhaving a pulse duration of approximately in the range of 0.05milliseconds to 2 milliseconds; generating a right ventricular pacingpulse for a right ventricle having the pulse duration of approximatelyin the range of 0.05 milliseconds to 2 milliseconds; generating a leftventricular pacing pulse for a left ventricle having the pulse durationof approximately in the range of 0.05 milliseconds to 2 milliseconds;delivering the right atrial pacing pulse; discharging a right atrialrecharge pulse after completing the delivery of the right atrial pacingpulse such that it is non-overlapping with the right atrial pacingpulse; delivering the right ventricular pacing pulse such that it isapproximately in the range of 2 milliseconds to 10 milliseconds afterdelivering the right atrial pacing pulse, and after completing thedischarge of the right atrial recharge pulse; delivery the leftventricular pulse such that it is approximately in the range of 2milliseconds to 10 after delivering the right ventricular pacing pulse,and such that the right and left ventricular pacing pulses aresubstantially simultaneous and non-overlapping; and discharging rightatrial, right ventricular and left ventricular recharge pulses such thatthey are non over lapping, and further the discharging of the rightatrial, right ventricular, and left ventricular recharge pulses are nonoverlapping with the right atrial, right ventricular, and rightventricular pacing pulses.